British Heart Journal, I972, 34, 874-88I. Br Heart J: first published as 10.1136/hrt.34.9.874 on 1 September 1972. Downloaded from Duration of phases of left ventricular systole using indirect methods I: Normal subjects J. Fabian,' E. J. Epstein, and N. Coulshed From the Liverpool Regional Cardiac Centre, Sefton General Hospital, Liverpool The duration of the various phases of left ventricular systole has been measured in a series of So normal subjects using high speed simultaneous recordings of the electrocardiogram, the phono- cardiogram, the carotid pulse, and the apex cardiogram. The five phases of systole measured were: total electromechanical systole (Q-A2 interval); left ventricular ejection time (LVET); pre-ejection period (PEP); isovolumetric contraction time (IVCT); total mechanical systole (TMS). The Q-A2 interval, left ventricular ejection time, and total mechanical systole were linearly and inversely related to heart rate. The pre-ejection period and the isovolumetric contraction time were not significantly related to heart rate. The validity of the method has been substantiated by comparing simultaneous records ofdirect and indirect pulseforms in a small series ofpatients. The are and at heart rates showed no deviation findings reproducible serial daily studies different from copyright. the normal range. The results have been compared with those reported by various authors and they are in close agreement. Methods used to assess cardiac function, 2) Left ventricular ejection time (LVET). which depend on measurements ofintravascu- 3) Pre-ejection period (PEP). http://heart.bmj.com/ lar pressure and flow, are not readily per- 4) Isovolumetric contraction time (IVCT). formed in ambulant patients. The procedures 5) Total mechanical systole (TMS). are uncomfortable, carry some risk to the patient, and are not easily repeated. The results in normal subjects are presented The duration of the phases of left ventricu- to establish a normal range for comparison lar systole, which are potentially useful as with those in various cardiac disorders. In indices of left ventricular performance, can be addition, we have compared our findings with measured from accurately externally recorded those of other workers. on September 29, 2021 by guest. Protected pulse waves, and such externally recorded time intervals do not appear to differ signifi- cantly from those obtained by direct measure- Methods and subjects ment. Recent publications have described the Studies were performed on 5o normal healthy various techniques which can be used (Jezek, adults (35 men and I5 women) aged i8 tO 79 I963; Oreshkov, I965; Weissler, Harris, and years. Twenty-five were under 40 and 25 were Schoenfeld, i968; Spodick and over 40 years of age. The majority were members Kumar, of the hospital staff and the remainder were sur- i968a and b). gical patients admitted for relatively minor pro- This paper describes a method of recording cedures unrelated to the cardiovascular system. and measuring five important phases of left All subjects had a normal exercise tolerance, no ventricular systole, viz: cardiovascular abnormality on clinical examina- tion, a normal electrocardiogram, and were not i) The Q-A2 interval or total electromechani- on any form of medication. cal systole (TEMS). Simultaneous recordings were made of the electrocardiogram, the phonocardiogram, the Received 28 October 1971. apex cardiogram, and the right carotid arterial 'Present address: First Medical Clinic, Charles Uni- pulse using a multichannel oscilloscopic recorder versity, Vlasska 36, Prague x, Czechoslovakia. (Cambridge Instrument Company) and a paper Duration ofphases of left ventricular systole using indirect methods 875 Br Heart J: first published as 10.1136/hrt.34.9.874 on 1 September 1972. Downloaded from i) The total period of electromechanical systole or the Q-A2 interval. Defined as the interval from the onset of the Q wave of the electrocardiogram 2-e L to the onset ofthe first high frequency component of the aortic component of the second sound. 2) The left ventricular ejection time measured from the beginning of the carotid upstroke to the nadir of the carotid incisura. 3) The interval from the beginning of the up- stroke of the apex cardiogram to the onset of the carotid upstroke. 4) The delay in transmission ofthe central arterial pulse to the carotid artery, or the pulse trans- mission time, measured from the first rapid vibration of the aortic component of the second sound to the nadir of the carotid incisura. ;ii All intervals were calculated as the mean of I1 ( measurements made on at least five cardiac cycles, each read to the nearest 5 msec. Heart rate was ,FIG. i Normal subject: simultaneous records calculated from the average RR interval of the of the apex cardiogram (ACG), the carotid cycles measured. pulse (CP), the phonocardiogram (PCG), and The following intervals were calculated from lead II of the electrocardiogram. A = Q-A2 the above measurements. interval; B = left ventricular ejection time i) Pre-ejection period This was calculated (LVET); C= onset of ACG upstroke (u) to by subtracting the left ventricular ejection time onset of CP upstroke (u); D = A2 to dicrotic from the total period of electromechanical systole notch interval or pulse transmission time (Q-A2 interval). PEP = (Q-A2)- (LVET). This (PTT); E= total mechanical systole (TMS); is the same as the interval from the onset of the copyright. A minus B =pre-ejection period (PEP); Q wave of the electrocardiogram to the onset C minus D = isovolumetric contraction time of the carotid upstroke corrected for the pulse transmission (IVCT); S1=first heart sound; A2, P2 = delay. aortic and pulmonary components of the second 2) Isovolumetric contraction time (IVCT) heart sound; 2L = second left intercostal space The interval from the beginning of the upstroke parasternally; MF= medium frequency. Time of the apex cardiogram (ACGu) to that of the are at msec klines 40 intervals. carotid pulse (CARu) corrected for the delay in http://heart.bmj.com/ transmission of the central arterial pulse to the carotid artery (PTT) (Oreshkov, I965; Spodick and Kumar, i968a). IVCT=ACGu to CARu- speed of IOO mm/sec (Fig. I). The recordings PTT. were performed in a similar fashion to the routine phonocardiographic practice of this Unit (Coul- 3) Total mechanical systole (TMS) The shed and Epstein, I963). Usually standard lead II sum of isovolumetric contraction time (IVCT) of the electrocardiogram was employed. A crystal and left ventricular ejection time (LVET). microphone to record the heart sounds was placed TMS=IVCT+LVET. This is the same as the parasternally in the second or third left interspace. interval from the beginning of the upstroke of the on September 29, 2021 by guest. Protected Occasionally two microphones were used in order apex cardiogram to the aortic component of the to identify the aortic and pulmonary components second heart sound (A2). of the second sound. The right carotid arterial The results on the 50 subjects were statistically pulse and apex cardiogram were recorded using evaluated (Croxton, 1959). Standard deviations funnel-shaped pick-ups with an internal diameter and regression equations were calculated to relate ofapproximately I *5 cm. The funnels were connec- heart rate to systolic time intervals. ted to identical piezoelectric crystal microphones In ii patients with various cardiac disorders a %by similar lengths of rigid plastic tubing less than Telco micromanometer was placed in the central 2 feet in length. There was no time lag between aorta and left ventricle during a diagnostic study. the two recording systems. Records were taken Simultaneous records were made of the carotid with the breath held in partial expiration and with pulse and the central aortic pressure curve in 7 the patient in a semi-left lateral position, in order patients and of the apex cardiogram and the left to bring the apex impulse against the chest wall. ventricular pressure curve in 7 patients. Three of Identification of the underlying zone of the ven- these patients had both aortic and then left ven- tricle was accomplished by recording a unipolar tricular pressures recorded with the carotid pulse -electrocardiogram lead at the site of the apex and the apex cardiogram, respectively. Experi- cardiogram. mental studies showed that there was no signifi- The following intervals were measured directly cant time lag between the Telco micromanometer from the tracing (Fig. i). and the external pulse microphone. 876 Fabian, Epstein, and Coulshed Br Heart J: first published as 10.1136/hrt.34.9.874 on 1 September 1972. Downloaded from Results electrocardiogram, the phonocardiogram, the These are shown in Table and Fig. 2. carotid pulse, and the apex cardiogram. With a fast recording speed of IOO mm/sec, mea- i) Q-A2 interval or total electro- surements can be made within an accuracy of mechanical systole (TEMS) The mean about 5 msec. Braunwald, Sarnoff, and Stainsby (I958) Q-A2 interval was 382 ± 23 msec with a range of 330 to 440 msec. There was a close linear studied left ventricular ejection time in an iso- relation between the Q-A2 interval and heart lated dog heart preparation. They found that rate (Fig. 2). The regression equation was increasing the stroke volume at a fixed heart rate increased the ejection time, whereas in- Y= + 503-I *59 HR (r= -0 79; P < OOOI). creasing the heart rate with a fixed stroke 2) Left ventricular ejection time (LVET) volume shortened the ejection time. Wallace The mean LVET was 28I ±2I msec with a et al. (I963) studied in more detail the various range of 230 tO 334 msec. There was a close phases ofleft ventricular systole in dogs. They linear relation between the LVET and heart showed that increasing the stroke volume at rate (Fig. 2). The regression equation was a fixed heart rate prolonged the ejection time, Y = + 389-I14I HR (r = -078; P <oooi). shortened isovolumetric contraction time, and had little effect on total systole.